The properties of semiconductor devices, particularly thin film transistors (TFTs), may be degraded in certain environments. Thus, suitable encapsulate materials have been sought. Of particular interest is the encapsulation of organic semiconductor devices because of their compatibility with potentially cost-effective non-glass substrates. Conformal coatings have been applied to organic transistor devices to protect against device degradation. The coatings, however, may cause decreased device performance and failure. Possible mechanisms include chemical degradation, traps introduced by coatings and delamination of semiconductor films and/or drain and source electrodes. Furthermore, many encapsulants suitable in conventional applications tend to require a high deposition temperature that is near or above the melting temperature of the organic TFT elements. Thus, there is a need for an encapsulant that is capable of being formed at a low enough temperature and also is able to provide the necessary encapsulating properties.
Techniques for enhancing the semiconducting properties of organic semiconductor materials, such as annealing in particular environments, have been explored in the art. Two methods have been found useful in lowering a transistor's off-current while keeping field-effect mobility substantially unchanged. In the first method, the films are treated with ammonia by bubbling N2 through ammonium hydroxide aqueous solution. The same method has been used to change the resistivities of conducting polymers. Thermal treatments, such as heating the samples under N2 at 100° C. for five minutes, can also lower off-currents. However, upon removing the device from the annealing or ammonia environment, such enhancements seem to substantially disappear in a time-dependent fashion. Accordingly, there is a need to create and maintain such enhancements.